Question

A sample of hydrazine sulphate (\[{N_2}{H_6}S{O_4}\]​) was dissolved in \[100\;mL\;\] of water. \[10\;mL\;\] of this solution was reacted with an excess of \[FeC{l_3}\] ​ solution and warmed to complete the reaction. Ferrous ion formed was estimated and it required \[20\;mL\;\] of $\dfrac{M}{{50}}KMn{O_4}$ ​. Estimate the amount of hydrazine sulphate in one litre of solution.
Reactions: \[4F{e^{3 + }} + {N_2}{H_4}\, \to {N_2}\, + \,\,4F{e^{2 + }} + \,\,4{H^ + }\]
\[MnO_4^ - + \,\,5F{e^{2 + }} + \,\,8{H^ - } \to M{n^{2 + }} + \,\,5F{e^{3 + }} + \,\,4{H_2}O.\]

Answer 1

Hint:To calculate the amount of Hydrazine Sulphate that’s gets dissolved in one litre of solution, we will compare the Equivalent mass of hydrazine Sulphate (\[{N_2}{H_6}S{O_4}\]) with equivalent mass of potassium permanganate ($KMn{O_4}$ ).

Complete step by step answer:
Given redox reactions:
\[4F{e^{3 + }} + {N_2}{H_4}\, \to {N_2}\, + \,\,4F{e^{2 + }} + \,\,4{H^ + }\]
\[MnO_4^ - + \,\,5F{e^{2 + }} + \,\,8{H^ - } \to M{n^{2 + }} + \,\,5F{e^{3 + }} + \,\,4{H_2}O.\]
The redox changes are as follows:
For \[FeC{l_3}\]: $F{e^{3 + }} \to \,F{e^{2 + }} + 1e$
For \[{N_2}{H_6}S{O_4}\]: $N_2^{2 - } \to {N_2} + 4e$
Now, we will compare the equivalent mass of Potassium permanganate and equivalent mass of Hydrazine Sulphate in \[10\;mL\;\] solution:
${M_{eq}}\,{N_2}{H_6}S{O_4} = {M_{eq}}\,KMn{O_4}$
The molar mass of hydrazine sulphate is $130\,g$ and the change in oxidation is 4 so its n factor will be $4$.
As the n factor is $4$the equivalent Mass of Hydrazine Sulphate will be$ = \dfrac{{130}}{4} = 32.5$
Now, we will calculate the amount of hydrazine present in \[10\;mL\;\] solution. So the amount will be;
$Amount\,of\,hydrazine = \dfrac{1}{{10}} \times \dfrac{{32.5}}{{1000}} \times 20 = 0.065\,g$
Now, with this, we will calculate the amount of hydrazine sulphate present in one litre of solution. It will be;
$Amount\,of\,hydrazine\,in\,1l\,solution = \dfrac{{0.65}}{{10}} \times 1000 = 6.5\,g$
Hence, the amount of hydrazine sulphate required in one litre of solution will be $6.5\,g$.

Additional information
Hydrazine sulphate is a salt of the hydrazinium cation and the anion of bi-sulfate. It is a water-soluble white salt. It is used as a catalyst in fiber making from acetate. It is also used industrially as jet fuel and in the treatment of cancer. \[{N_2}{H_6}S{O_4}\] can also be used as a fungicide and antiseptic. You can also prepare \[{N_2}{H_6}S{O_4}\] by reacting hydrazine with sulphuric acid.

Note:
$KMn{O_4}$ or Potassium permanganate is an organic compound. It is used as an oxidizing agent. It is a purple-black crystalline solid in colour. It reduces itself and oxidizes the other compounds. It is soluble in water and is also used for cleaning of wounds.